Fix post blank for comment.

src/types/lesser_element.rs

@@ -35,6 +35,7 @@ pub struct Paragraph<'s> {
 pub struct Comment<'s> {
     pub source: &'s str,
     pub value: Vec<&'s str>,
+    pub post_blank: Option<&'s str>,
 }
 
 #[derive(Debug)]
@@ -242,7 +243,11 @@ impl<'s> StandardProperties<'s> for Comment<'s> {
     }
 
     fn get_post_blank(&self) -> PostBlank {
-        0
+        self.post_blank
+            .map(|text| text.lines().count())
+            .unwrap_or(0)
+            .try_into()
+            .expect("Too much post-blank to fit into a PostBlank.")
     }
 }